Generally, bitumen is a viscous, black and sticky organic liquid that may be soluble in carbon disulfide. In some instances, bitumen can be obtained as a mixture of condensed polycyclic aromatic hydrocarbons by fractional distillation of crude oil. Bitumen is generally the fraction with the highest boiling points from the fractional distillation. In some instances, bituminous materials, such as asphalt, can comprise bitumen and at least one other substance, such as an additive.
There are many applications for bitumen and/or various asphalt compositions. For example, they can be used for waterproofing products or articles, such as roofs, buildings, boats, shingles, roofing felts, roofing sheets or roofing membranes, as well as for paving roads, rail beds, runways, running tracks, greenway trails, playgrounds, bicycle and golf cart paths, racetracks, basketball and tennis courts, driveways, subdivision roads, animal feed lots, poultry house floors, barn floors, greenhouse floors, work sites, log yards, ports, freight yards, landfill caps and the like. Furthermore, bitumen and various asphalt compositions can be used in fish hatcheries, reservoir liners, industrial retention ponds, sea walls, dikes and groins.
Bitumen and asphalt can be modified chemically or physically for various applications, each of which requires certain desirable properties. For example, modified bitumen (MB) is bitumen modified by additives to give it plastic or rubber-like properties. Some modified bitumen sheets or membranes can be used in low slope roofing for commercial and large buildings. Modified bitumen may also be utilized in roofing sheets or waterproofing membranes.
Asphalt shingles are generally the primary roofing materials for residential graded roofs. Asphalt shingles may comprise either organic felt materials or glass fiber reinforcing mats which are saturated or encapsulated with bitumen or asphalt to make them waterproof. In general, asphalt shingles are for steep slope roofing whereas modified bitumen membranes are for low slope roofing.
The largest use of bitumen or asphalt is for making asphalt concrete for paving roads. Such use accounts for approximately 80% of the asphalt consumed in the United States. Roofing accounts for most of the remaining asphalt consumption. Asphalt concrete generally comprises a bituminous binder, limestone aggregate, and sand matrix. Mastic asphalt, which can also be used for paving roads, differs from asphalt concrete in that the former has a higher bitumen content that the latter. Generally, mastic asphalt contains about 7-10 wt. % of bitumen, whereas asphalt concrete has about 5 wt. % of bitumen. Another asphalt useful for paving roads is stone mastic asphalt, which is becoming popular because of its high anti skid qualities and improved durability.
Attempts have been made to mix bitumen and asphalt with a wide range of polymers for various applications including roofing and paving. Such polymers include atactic polypropylene (APP) and styrene block copolymers (SBS) (e.g., styrene-butadiene-styrene (SEBS), styrene-isoprene-styrene (SIS), and styrene-ethylene-butadiene-styrene block copolymers (SEBS)). Unfortunately, it takes a relatively long time to process or dissolve the above-mentioned polymers in bituminous materials such as bitumen or various asphalt compositions. Further, these polymer modifiers can be degraded or aged by heat, UV light, weather or a combination thereof. Attempts have also been made to mix rubbers such as EPDM with asphalts. See, e.g., U.S. Pat. Nos. 4,069,181; 4,738,997 and EP Patent Nos. 0338336 A1; 02011671B1; and 0093500 A1. Additional rubber compositions are described in U.S. Pat. Nos. 3,873,483; 4,129,542; 6,414,056; U.S. Publication Nos. 2006/0243163; 2006/0249049; and European Application No. EP 0775719 A2. Unfortunately, the mixing often proves difficult.
Therefore, there is a need to develop new polymer compositions for improving the heat and UV stabilities properties of bituminous materials for various applications including roofing and paving. Further, there is a need to reduce the time required to process or dissolve polymers in the bituminous materials and facilitate mixing to form a stable product.
The present invention meets at least the aforementioned needs and in one embodiment provides a composition comprising ethylene/alpha-olefin interpolymer and a bituminous material, wherein the interpolymer optionally comprises at least one diene. The interpolymer is typically derived from polymer particles having a surface coating comprising a partitioning agent wherein the mean particle size of the polymer particles is less than about 3 mm. The present invention also provides a process for preparing a composition, wherein the process comprises dissolving an ethylene/alpha-olefin interpolymer, wherein the interpolymer optionally comprises at least one diene, in a bituminous material. The interpolymer is typically derived from polymer particles that have a surface coating comprising a partitioning agent wherein the mean particle size of the polymer particles is less than about 3 mm. The present invention also provides a process for preparing an article, wherein the process comprises dissolving an interpolymer comprising ethylene, at least one alpha-olefin, and at least one diene in a bituminous material. In another embodiment, one or more of the unreacted double bonds in the interpolymer are further chemically modified in situ in the process to produce the article.